Thursday, June 3, 2010

Farming out the work

I finally got back to the hangar today to start riveting on the fuselage belly skin. I had a few distractions over the last couple of days that kept me from getting to it, but one of them was very educational with regards to RV-12s.

There's an RV-12 over at Lancaster International Airport that is just about ready for first flight. In fact, it was scheduled to be inspected today and hopefully be rewarded with the certificate that will define it as an actual airworthy flying machine. I hope to hear whether everything went well in the next day or two. My involvement was in applying a firmware update to the Dynon D-180 FlightDek box.

"Just one second there, Mister," you're thinking, "What's a Dynon D-180 FlightDek? And what in the world is firmware??"

Good questions, those. I'll start with the D-180. The D-180 is a computer. It's a computer with a very specific purpose, though, as opposed to the computer you're using to read this blog which can do any number (approaching infinity) of different things. The D-180 is a computer that is very rigid in what it can do. You can't add new programs to it that will allow you to play strip Solitaire, you can't use it to browse the internet looking for the best recipe to prepare possum stew, and you can't use it to sign people you don't like up to receive sales emails from Amway Global. It does one thing: it provides a display of what the airplane is doing. It replaces umpteen mechanical instruments with one LCD display.

I should warn you that the language used in that video is High Gibberish, the native language of New Gibber.

Turn down your speakers.

Computers are essentially pieces of electronic 'hardware' that are made useful by virtue of being able to run 'software.' The hardware is the mechanical, tangible stuff, and the software encompasses all of the programs that run on the computer hardware. Somewhere in between is 'firmware' - think of it as partially melted ice cream. It's not quite ice cream, but it's not quite sickly-sweet flavored milk, either.

Ah, what the heck. Maybe Professor Wick. E. Pedia can explain it better:

There are no strict boundaries between firmware and software, as both are quite loose descriptive terms. However, the term firmware was originally coined in order to contrast to higher level software which could be changed without replacing a hardware component, and firmware is typically involved with very basic low-level operations without which a device would be completely non-functional. Firmware is also a relative term, as most embedded devices contain firmware at more than one level. Subsystems such as CPUs, flash chips, communication controllers, LCD modules, and so on, have their own (usually fixed) program code and/or microcode, regarded as "part of the hardware" by the higher-level(s) firmware.

Simple firmware typically resides in ROM or OTP/PROM, while more complex firmware (often on the border to software) typically employs flash memory to allow for updates, at least in modern devices. Common reasons for updating firmware include fixing bugs or adding features to the device. Doing so usually involves loading a binary image file (provided by the manufacturer) into the device, according to a specific procedure; this is sometimes intended (by the device manufacturer) to be done by the end user.

Yep, clear as mud!

All you really need to know is that firmware has a distinct and critically important advantage over hardware: it can be updated and changed relatively easily. So, for example, let's hypothetically say that Dynon made a mistake in their programming and the oil pressure was indicating in units of metric tons per square peg instead of the more traditional pounds per square inch. Rather than having owners remove their D-180 and send it back to the factory for correction, they simply update the firmware. Simple, as always with these things, being a relative term.

This is where I come in. As part of the preparation for flight, the firmware in the D-180 in question needed to have the latest firmware updates applied. This is done by downloading the firmware file from an internet site onto a laptop computer. The laptop is then carried out to the airplane and plugged into the D-180. With that connection made, the firmware is copied from the laptop and into the D-180. Not everyone is comfortable with this kind of thing, but I take to it like a cat to water so I was invited to give it a try. I'm not sure why, but I think it's a form of stereotyping ageism. Japanese tourists take pictures, the Irish are heavy drinkers, and people under fifty know everything there is to know about computers.

I live to disprove stereotypes.

I had no trouble downloading the new firmware. I even knew to also download the device driver for the serial-to-USB converter. You 50+ year old readers can just stop here if this is all gibberish to you.

Oh, ok.

In computing, a device driver or software driver is a computer program allowing higher-level computer programs to interact with a hardwaredevice.

A driver typically communicates with the device through the computer bus or communications subsystem to which the hardware connects. When a calling program invokes a routine in the driver, the driver issues commands to the device. Once the device sends data back to the driver, the driver may invoke routines in the original calling program. Drivers are hardware-dependent and operating-system-specific. They usually provide the interrupt handling required for any necessary asynchronous time-dependent hardware interface.

See? Pure gibberish.

Long story short (Ha ha ha! It's WAY too late for that!), it didn't work. I plugged the cable into the laptop on one end and into the D-180 on the other. I started the program that I had downloaded. It was supposed to detect the D-180 and update the firmware.

It said "Hey! Nothing there!!"

I said "Aww, crap."

I diddled around with it - no help.

We called Dynon tech support.

"Well, that ought to work. Is the computer even detecting the cable?"

"Nope," I replied.

"Huh. That's odd. Try putting the cable in a different socket."

I tried all three of the available USB ports. (Oh, for crying out loud. Just go to Google and look up 'USB' yourself)

No luck. Steadfast silence from the laptop. The kind of ominous silence you get when you answer the "Does this dress make my butt look big" question wrong. Another ten minutes of commiserating with the tech support guy over the deplorable state of Microsoft Windows later, we (and by "we" I mean "me") were ready to give up.

That's when I noticed that I was putting the USB plug in upside down, a feat that I didn't even know was possible. Note that I did not shout out "Eureka! Here's the problem!!" No, I quietly and meekly turned the plug over right side up and plugged it in again when no one was looking rather than share my burning shame with the tech support guy.

Still didn't work.

In a way, that was kind of a relief. It meant that the twenty minutes I spent with the plug in upside down wasn't the actual problem. Still, it was the last straw. I shut down the laptop and prepared to head home with my tail between my legs in ignominious defeat. Then it hit me, and it pains me that I've known and lived this for twenty years yet failed to think of it sooner: the first thing you do when Windows doesn't work is reboot the computer.

I turned the laptop back on.

It worked.

You know, even if a magic trick doesn't work the first time, it's still magic to the people watching when you finally do get it to work.

At least I hope that's the case.

So, finally, I got back to the hangar to do some riveting on my airplane today. The CEO came in to help.

We ran out of time before we ran out of rivets to pull, but I think we got a good 2/3s of them done. I'll knock out the rest tomorrow and haul the whole enchilada back to the basement shop for the next steps. I like the mass riveting jobs because they're great for letting other people participate in the building. The learning curve for using the rivet puller is something like "two rivets from zero to full proficiency," and it's work that will always be visible when the plane is done. I think it's really nice that people that have come by to help will see the completed airplane someday and be able to point to the area that they built.

Well, in this case by having to bend over and look underneath, but still....

Thanks for the post, very informative as always. I noticed that the video mentions the display of angle-of-attack information. Is there an actual AoA sensor, is the information computed by the computer from other variables, or is it just a generic feature of D-180 that's not used in the RV-12?

By the way, do you know whether you'll go for glass cockpit or round dials?

The angle-of-attack indication requires an optional pitot tube that has a few extra holes drilled in it to allow it to sense AoA. The D-180 package as provided by Van's for the RV-12 does not use that special pitot tube. The reason for that is on the RV-12, the pitot tube is not in the traditional location out on a wing; the removable wings would make the connection difficult. Instead, the pitot tube runs through the hollow prop shaft and out through the middle of the prop spinner.

To build the RV-12 under the E-LSA rules, you have no decisions to make - the plane has to be built exactly like the factory model. That means that I have no choice but to use the D-180. That's fine by me as I think I would have made the same decision myself, although I might have opted for the newer Dynon SkyView.

You can also build an RV-12 under the old Experimental Aircraft rules. If you decide to do that, anything goes. You could use mechanical instruments instead of glass. I'm not sure why anyone would, though. You would have to completely rebuild the panel and avionics trays, design and wire your own electrical system, and buy a bunch of not-all-that-cheap mechanical gauges, all in favor of ending up with a less capable airplane.

2 comments:

Thanks for the post, very informative as always. I noticed that the video mentions the display of angle-of-attack information. Is there an actual AoA sensor, is the information computed by the computer from other variables, or is it just a generic feature of D-180 that's not used in the RV-12?

By the way, do you know whether you'll go for glass cockpit or round dials?

The angle-of-attack indication requires an optional pitot tube that has a few extra holes drilled in it to allow it to sense AoA. The D-180 package as provided by Van's for the RV-12 does not use that special pitot tube. The reason for that is on the RV-12, the pitot tube is not in the traditional location out on a wing; the removable wings would make the connection difficult. Instead, the pitot tube runs through the hollow prop shaft and out through the middle of the prop spinner.

To build the RV-12 under the E-LSA rules, you have no decisions to make - the plane has to be built exactly like the factory model. That means that I have no choice but to use the D-180. That's fine by me as I think I would have made the same decision myself, although I might have opted for the newer Dynon SkyView.

You can also build an RV-12 under the old Experimental Aircraft rules. If you decide to do that, anything goes. You could use mechanical instruments instead of glass. I'm not sure why anyone would, though. You would have to completely rebuild the panel and avionics trays, design and wire your own electrical system, and buy a bunch of not-all-that-cheap mechanical gauges, all in favor of ending up with a less capable airplane.

Post a Comment

N284DG

About Me

Testimonials

"Your writing reminds me of someone you may be too young to appreciate - Gordon Baxter." -- Richard Collins

"I wish.... I could write like you. Oh good God can you paint a picture with words! I have been a fan for years!"

"Said it before. Saying it again. Dave Gamble is one of the greatest writers I've ever read."

"Dave Gamble can wrap words around the story like no other ..."

"I have been reading and totally enjoying your writing for years."

"One of my favorite flying blogs, besides my own of course, is Schmetterling Aviation. I like it mostly because I love to read Dave’s writing. He has a mastery of vocabulary coupled with a great sense of humor that keeps me coming back."

"I solved the problem with help of an excellent builder's web site. Thanks to Schmetterling Aviation's well documented build log."

"I HIGHLY recommend Schmetterling Aviation.com as both thorough and entertaining."

"You have such a great flair for transforming the mundane into an informative, yet humorous read."